Ozone resistant compositions

ABSTRACT

THE INCORPORATION OF UNITS DERIVED FROM A C5 TO C110 POLYOLEFIN HAVING TWO POLYMERIZABLE DOUBLE BONDS SAID UNITS BEING PRESENT IN AN AMOUNT RESULTING FROM THE ADDITION TO THE REACTION MIXTURE FROM WHICH THE COPOLYMER IS FORMED OF FROM 0.01 TO 0.5 GRAM-MOLES/KG. OF COPOLYMER FORMER OF SAID C5-C110 POLYOLEFIN OR IN EPDM ELASTOMER PRODUCED CHAIN BRANCHING, WITH A CONSEQUENT IMPROVEMENT IN PROPERTIES SUCH AS COLD-FLOW OF THE UNCIRED STOCK, AND IMPROVED OZONE RESISTANCE OF NATURAL RUBBER OR SYNTHETIC DIENE BLENDS.

United s es Patent Ofice 3,817,884 Patented June 18, 1974 3,817,884OZONE RESISTANT COMPOSITIONS John B. Campbell, Hockessin, and RobertDean Thurn, Wilmington, Del., assignors to E. I. du Pont de Nemours andCompany, Wilmington, Del.

No Drawing. Application May 19, 1970, Ser. No. 38,862, which is acontinuation-in-part of application Ser. No. 625,598, Mar. 24, 1967,both now abandoned. Divided and this application Apr. 17, 1972, Ser. No.244,886

Int. Cl. C08d 9/04 US. Cl. 260- 12 Claims CROSS-REFERENCE TO RELATEDAPPLICATIONS This is a Division of application Ser. No. 38,862, filedMay 19, 1970 which, in turn, is a continuation-in-part of applicationSer. No. 625,598 filed Mar. 24, 1967 both now abandoned.

BACKGROUND OF THE INVENTION This invention relates tosulfur-vulcanizable, chain-saturated elastomeric, a-olefin copolymershaving improved cold-flow. More particularly this invention relates toimproving the ozone resistance of blends of chain-unsaturated dienepolymers with sulfur vulcanizable, chainsaturated, elastomeric m-olefincopolymers by the introduction of a controlled amount of chain branchinginto the a-olefin copolymer.

Among the polymers of the aliphatic olefins that are made by use ofcoordination complex compounds of the transition metals aspolymerization initiators, the amorphous copolymers of ethylene withhigher alpha-monoolefins constitue an important class because of theirdesirable elastomeric character and their generally excellent resistanceto ozone and other chemicals. The chemical inertness of these polymersis attributed to the fact that the linear chain or backbone is acompletely saturated structure without the reactive double bonds of thecommon elastomeric materials such as natural rubber or the syntheticelastomers made from conjugated diolefins. This chemical inertness madethe early polyolefin elastomers, namely amorphous ethylene-propylenecopolymers, impossible to vulcanize with the sulfur systems preferred inthe rubber industry. This problem was solved by incorporating as thirdmonomers, non-conjugated diolefins containing both a readilypolymerizable and a relatively nonpolymeri'zable double bond, thusforming an elastomeric polymer consisting of a linear saturated backbonehaving pendant unsaturated hydrocarbon groups capable of participatingin crosslinking reactions with sulfur curing systems. The use ofnon-conjugated aliphatic diolefins such as 1,4-hexadiene and6methyl-l,5-heptadiene as the third monomer in hydrocarbon elastomers ofthis sort is taught, for instance, in US. Pat. 2,933,480, and the use ofbridged ring diolefins having double bonds of unequal reactivity issimilarly taught in US. Pat. 3,211,709.

It is the nature of coordination complex polymerization of olefinhydrocarbons to form practically linear, unbranched polymer chains.While a strictly linear polymer structure is advantageous in the stiff,crystalline polyolefins used as thermoplastic molding materials, such aspolyethylene and polypropylene, it is not necessarily so in amorphouspolyolefins that are used as elastomers. As a matter of fact, it hasbeen found that strictly linear polyolefin elastomers show relativelyundesirable cold-flow properties unless the polymer has an especiallybroad distribution of molecular weights. For example, the undesirablecold-fiow properties cause the elastomer to rupture bags in which theyare packaged during storage. However, such a distribution of molecularweight causes undesirably high viscosity of dilute solutions of thepolymer in the solvents employed in their manufacture and use.

DESCRIPTION OF THE INVENTION The present invention provides sulfurcurable chainsaturated branched elastomers comprising amorphouscopolymers consisting essentially of (a) from 25 to by weight ofethylene units,

(b) units derived from a C to C polyolefin containing two polymerizabledouble bonds, said polyolefin units being present in an amount resultingfrom the addition to the reaction mixture from which said copolymer isformed of about from 0.01 to 0.5 gram mole per kilogram of copolymerformed of said C -C polyolefin, not to exceed 15% by weight of thecopolymer, and

(c) sutficient units of a nonconjugated diolefin containing only onepolymerizable double bond to provide 0.1 to 4.0 gram mole/kilogram ofpolymer of carbon-carbon double bonds derived from the diolefincontaining one readily polymerizable double bond; and

(d) the remainder of said polymers being propylene units,

said polymers being prepared by an organo-soluble coordination catalyst.

The present invention also provides a sulfur curable ozone resistantcomposition consisting essentially of about 10 to 30 parts by weight ofthe copolymer of this invention and about to 70 parts by weight of apolyunsaturated elastomer.

As used herein, the term consisting essentially of has its generallyaccepted meaning as requiring that specified components be present, butnot excluding unspecified components which do not materially detractfrom the basic and novel characteristics of the composition asdisclosed.

Methods for carrying out the polymerization of olefin hydrocarbons withcoordination complex catalysts are well known in the art. See, forinstance, Linear and Stereo-regular Addition Polymers, by Gaylord andMark, Interscience Publishers, New York, 1959. Among the most usefulcatalyst systems for making elastomeric copolyolefins are those based onsoluble compounds of vanadium such as vanadium oxytrichloride, vanadiumtetrachloride, vanadium tris-(acetylacetonate), etc., used in conjuctionwith organoaluminum compounds such as aluminum alkyls (e.g.,t-riisobutyl aluminum), and alkyl aluminum halides (e.g., diisobutylaluminum chloride), and so on. It is preferable that a halogen bepresent on at least one of the catalyst components. Many variations andrefinements of these catalyst systems are now well known in the art. Theparticular organo-soluble catalyst system used is not critical to thepractice of this invention as long as it is capable of formingpractically amorphous copolymers of olefin hydrocarbons.

A variety of solvents can be employed with the catalyst. Among the mostuseful are tetrachloroethylene, and aliphatic hydrocarbons such ashexane. Other solvents will be apparent to those skilled in the art.

Methods for copolymerizing ethylene and propylene to form amorphouspolymers that have the basic charac' teristics of a synthetic rubber arewell known in the art. The principle of making such polymersvulcanizable with sulfur curing systems by introducing as a thirdpolymerizable monomer a multiolefin having only one polymerizable doublebond is also known. Polymerizable double bond is also known.Polymerizable double bonds in coordination polymerization systems aregenerally found to be unhindered terminal double bonds in aliphaticolefins, or double bonds in strained ring cycloaliphatic compounds, suchas cycloaliphatic compounds having oneor two-carbon bridged ringstructures. Double bonds that are found not to be readily polymerizableare generally the internal, i.e., nonterminal double bonds of aliphaticolefins, sterically hindered double bonds of aliphatic olefins such asthose carrying a methyl group or other substituent on one of the doublybonded carbon atoms, and double bonds in relatively unstrainedcycloaliphatic rings. Typical non-conjugated diolefins containing onlyone polymerizable double bond that are suitable in copolymers of thisinvention are 1,4-hexadiene, 2- methyl-1,5-hexadiene, 1,9-octadecadiene,6-methyl-1,5- heptadiene, 7-methyl-1,6-octadiene,11-ethyl-1,11-tridecadiene, and the like. Typical cycloaliphaticcompounds that can serve the same purpose include dicyclopentadiene,tricyclopentadiene, -ethylidene-2-n0rbornene, 5- methylene-Z-norbornene,alkenyl substituted norbornenes having an internal double bond in thealkenyl group (e.g., 5-(2'-butenyl)-2-norbornene), unsaturatedderivatives of bicyclo (2,2,2)-octane, and so on. The use of suchcompounds to provide pendant sulfur-reactive unsaturated structures onan amorphous polyolefin is well known in the art.

Amorphous copolyolefins including ethylene, propylene, and one or moreof the above-mentioned diolefins made by the prior art methods aremainly straight-chain polymers and have the disadvantages alreadymentioned.

A desirable ramification, i.e. chain branching, can be introduced intopolymers of the general class by including a carefully selectedproportion of a fourth monomer that has two polymerizable double bonds.As used herein, the term polymerizable double bond is meant terminal,unhindered double bonds in the main chain structure of the monomer, andthe double bonds in strained ring cycloaliphatic structures. Suitablemonomers may contain two terminal double bonds, two strained ring doublebonds, or one of each.

The monomers generally suitable for incorporation as the fourth monomerare C to C polyolefins. The amount of the polyolefin is not to exceed15% by weight of the copolymer. Incorporation of larger amounts ofpolyolefin produces a copolymer which yields an impractical curingformulation. For example, whereas 2 to 4 parts of sulfur are generallyrequired to cure an EPDM elastomer, 8 to 10 parts of sulfur may berequired when the polyolefin in the copolymer of this invention exceedsweight percent.

Typical monomers suitable for this purpose are 1,4- pentadiene,1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, 1,20-heneicosadiene,5-(5-hexenyl)-2-norbornene, 5-(2- propenyl)-2-norbornene, and the like.A particularly suitable diolefin having two strained ring double bondsis the reaction product of norbornadiene-2,5 and cyclopentadiene havingthe following structure For simplicity, this compound will be callednorbomeo norbornene, although its systematic name is 1,4,4a,5,8,Sa-hexahydro 1,4,5,8 dimethano-naphthalene. Compounds similar butresulting from the addition of more 4 bridged ring units by furthercondensation with cyclopentadiene can also be used, such as etc.

2,5-norbornadiene can be used, and the dimer thereof, which can berepresented by the formula with each radical furnishing onepolymerizable double bond when terminally located. Particularly suitableare compounds of the following formula:

where R is (CH with x=0-29, or phenylene, alkyl substituted phenylenes,naphthalene, polybutadiene, polyisoprene, polystyrene,poly-a-methylstyrene, butadienestyrene copolymer, butadiene-isoprenecopolymer, isoprene-styrene copolymer, or polyvinylnaphthalenes.

When esters, ethers, or any monomer containing a hetero-atom, such asoxygen, sulfur or nitrogen, are prescut during polymerization, it ispreferable to complex the hetero atom to facilitate polymerization. Thisis conveniently accomplished by using an excess amount of organoaluminumcompound in the coordination catalyst system as will be apparent tothose skilled in the art.

Analysis of the amount of monomer having two polymerizable double bondsincorporated in the polymer has in some cases proved difiicult. Theproportions described herein and in the following examples are theproportions employed in the synthesis. During the synthesis, it ispreferred that the conversion of the diolefin containing only onepolymerizable double bond be at least 20 percent. Also, it is preferredthat the conversion of the polyolefin containing two polymerizabledouble bonds be at least 20 percent; as conversion is increased, asmaller amount of the polyolefin is required to obtain the desiredbranching.

In the case of linear diolefins containing two terminal allyl groups theetficiency of the diterminal olefin as a modifying agent appears toincrease with chain length to about 8 carbon atoms. Diterminal olefinshaving 8 or more carbon atoms are most eflicient. It is accordinglypreferred to employ a-w-diolefins containing from 8 to 35 carbon atomsas the modifying agent.

The branched copolymers of the present invention consist essentially oflinear chains or backbones with branching along the chains. Thesebranched copolymers differ from previously known EPDM copolymers havinga practically linear structure. Chain branching is demonstrated by thefact that the copolymers of this invention have physical propertiessubstantially different than those of practically linear copolymers,such as known EPDM copolymers. The properties of the copolymer used todetect branching are the solution (inherent) viscosity and bulkviscosity as indicated by the Wallace plasticity. For example, theinherent viscosity and Wallace plasticity of a practically linearcopolymer and a branched copolymer are measured as described in thefollowing examples. The results are compared, and the branched copolymershows a greater rate of change in Wallace plasticity than the rate ofchange in inherent viscosity. Thus, for a given inherent viscosity, theWallace plasticity is greater for the branched than for the unbranchedcopolymer.

Mooney viscosity is measured at 121 C. in accordance with ASTM MethodD-1646-67 using the large rotor. After the sample has been warmed in themachine for one minute, the shearing disc viscometer motor is started tobegin the test. Four minutes later the reported viscosity reading istaken.

Wallace plasticity is a measure of the amount of flow or deformation ofunvulcanized elastomeric materials under load. The sample to be testedis sheeted and cut into pellets having a thickness in the range3.18-6.35 mm. (0125-0300 inch). The test is performed with a Wallaceplastimeter manufactured by H. W. Wallace and Co., Ltd., London. Duringa -second period the pellet is simultaneously compressed to exactly 1.0mm. in thickness and heated to 100 C., the resulting test piece is thensubjected to a 10 kg. load for exactly seconds at 100 C. The finalthickness of the test piece, expressed in units of 0.01 mm., is theplasticity 'value reported. The standard l-cm. diameter platen issuitable for pellets of average hardness. Proper platen temperatureregulation is most important because elastomer plasticity is usuallytemperature dependent. Plasticity readings should normally fall betweenand 90 on the scale for most reliable readings.

The elastomeric products of the present invention can be processed withconventional rubber processing equipment in the same way as other sulfurcurable a-olefin based elastomers, particularly those elastomers havinga broad molecular weight distribution.

Conventional compounding ingredients such as carbon black, mineralfillers, coloring agents, extending oils and the like are generallyincorporated into the polymers.

Various curing systems can be employed, as will be apparent to thoseskilled in the art. The most important of these curing systems is thesulfur curing system which is applicable to all of the polymers withinthe scope of this invention. Other curing systems include quinoid curingsystems, phenolic curing systems and peroxide curing systems.

The polymers of the present invention have improved cold flow resistancewhen isolated, compared with elastomers having the same proportions ofingredients and made with the same catalyst but omitting the modifyingamount of diolefin containing two polymerizable double bonds. The aboveimprovement is indicated by the increased Wallace Plasticity. As shownin the examples, the Wallace Plasticity of the Products can besubstantially increased without any substantial increase in solutionviscosity.

This invention is further illustrated by the following specificexamples. All parts, proportions, and percentages are by weight unlessotherwise indicated.

EXAMPLE 1 Production of Ethylene/Propylene/ 1,4-Hexadiene/ 1,7-

Octadiene Copolymer The following general procedure is used. A one-literresin flask is equipped with a stirrer, thermometer, a gas inlet tube, arubber (serum) cap and gas outlet tube. The

resin flask stirrer, gas inlet tube and gas outlet tube are dried in anoven at 65 C. and 105 mm. pressure for at least thirty minutes beforeuse. One-half liter of heptane which has been dried over silica gel andsparged with nitrogen is introduced into the resin flask along with 3.4ml. of 1,4-hexadiene. The rapidly stirred solvent is then presaturatedwith ethylene and propylene at flow rates of 1 and 2 liters/min,respectively, the feed stream being introduced below the surface of thesolvent. The flow of gases to the resin flask is then left unchangedthroughout the subsequent polymerization. The ethylene and propylene aremetered through separate rotameters at a back pressure of 3 p.s.i. andcombined at a three-way joint before being introduced into the resinflask. The ethylene and propylene are dried individually by passagethrough a two-foot high column of Molecular Sieve Type 5A. After thesolvent has been presaturated, a polymerization is initated byintroducing 5 ml. of a 1.0 Molar solution of diisobutylaluminum chloridein tetrachloroethylene and 5 ml. of a 0.1 Molar solution of vanadiumtrisacetylacetonate in benzene by means of hypodermic syringes. Theflask contents are kept at 25 C. by external cooling withDry-Ice-acetone bath for a period of thirty minutes, after which time 10ml. of a 1% solution of 4,4-thio bis(6- t-butyl-m-cresol) in isopropylalcohol is added to stop the polymerization.

1,7-Octadiene, a diolefin having two readily polymerizable double bonds,is added at a constant rate throughout the thirty-minute reactionperiod. The octadiene is conveniently handled in the following way: Asmall quantity of 1,8-octadiene, shown to be 97% pure by vapor phasechormatography, is passed through a short column of alumina, theefiiuent collected under nitrogen and the desired amount is accuratelyweighed into a volumetric flask where it is diluted with 200 ml. heptaneand stored under nitrogen. A control is prepared with no 1,7-octadiene.

After the reaction has stopped, the feed streams are shut off, and thepolymer solution is washed with 200 m1. of 5% hydrochloric acid untilthe organic phase is colorless. The organic layer is separated andwashed twice more with 200 ml. proportions of water. The solvent isallow to evaporate from the polymer solution in a porcelain pan. Thecopolymer produced is obtained as a thin film which is dried at 60C./105 mm. for 2436 hrs. The reaction is repeated three more times withvarying quantities of 1,7-octadiene. The results are described in TableI.

Propylene content is determined from the infrared absorption spectrum,and 1,4-hexadiene content is determined from the infrared absorptionspectrum or by bromine absorption. Inherent viscosity is determined on a0.1% solution of the polymer in tetrachloroethylene at TABLEL-E/P/1,4-HD/1,7-OCTADIENE COPOLYMERS a Control.

EXAMPLES 2-5 Production of Ethylene/Propylene/Hexadiene Copolymer WithVarious Dienes Having Two Readily Polymerizable Double BondsIncorporated Therein In a reactor as in Example 1 is placed 500 ml. oftetrachloroethylene which has been dried over silica gel and spargedwith nitrogen, and 3.8 ml. of 1,4-hexadiene. A combined stream ofnitrogen, ethylene, and propylene is introduced at flow rates of 0.5, 1,and 2 liters/ minute, respectively. Reaction temperature is C. Dienewith two readily polymerizable double bonds is then added as indicatedin Table H, and polymerization is initiated with 5 ml. of a 1.0 Molarsolution of diisobutylaluminum chloride and 5 ml. of 0.1 Molar vanadiumcompound as shown in Table II. The reaction is allowed to proceed for15-20 minutes, and the polymer is isolated as in Example 1.

Table II shows the desirable eifects on plasticity and cold flowproperties of several dienes having two readily polymerizable doublebonds. 1,4-Pentadiene and 1,7-octadiene are readily available diolefinsof this class. 1,20- Heneicosadiene is prepared fromheneicosa-1,20-dien-11- one by Wolf-Kishner reduction, the ketone havingbeen made from ll-undecenoyl chloride by the method of Sauer, J. Am.Chem. Soc., 69, 2444 (1947). The 5-(5- 8 EXAMPLE 6 Production ofEthylene/Propylene/5-Methylene- Norbornene/1,7-Octadiene Copolymer In areactor as in the previous Examples, using the procedure described inExamples 2-5, except at a reaction temperature of C., an ethylene,propylene, S-methylene-norbornene terpolymer is prepared. TheS-methylenenorbornene is added in the following Way: Two ml. of asolution consisting of 5.0 gm. of S-methylene-Z-norbornene in 110 m1. oftetrachloroethylene is added to the solvent before the catalyst andco-catalyst are added. The diisobutylaluminum chloride and vanadiumtrisacetylacetonate solutions are injected, and the polymerization isallowed to proceed for fifteen minutes during which time 18 ml. of themethylene norbornene solution is added dropwise at a constant rate. Thetemperature is kept at 25 C. throughout the polymerization. The reactionis stopped and the copolymer is isolated as in Examples 1-4. Thisproduct is the control of Table III.

The reaction is repeated except that just before the catalyst andco-catalyst are injected into the resin flask, an 0.052 Molar1,7-octadiene solution in tetrachloroethylene is added. Five ml. of thesolution is used in Example 6A, and 10 ml. in Example 6B. The resultsare summarized in Table III.

l Gram-moles of H C=CH- per kilogram of polymer.

hexenyl) norbornene is prepared by the method of US. Pat. 3,144,491.Vanadium components of the catalysts are vanadium trisacetylacetonate,V(AA) and vanadium oxytrichloride, VOCl The greatly increased bulkviscosity of the polymers with increasing incorporation of dienes withtwo readily polymerizable bonds, even though solution viscosity islittle afiected, is shown both by the Wallace Plasticity data and by theCold Flow data.

Cold flow is measured at 100-102 C. in the following manner. A device isassembled such that weighed brass cylinders (124-125 g., 19.5 mm. indiameter) freely sliding through holes in a one-inch iron plate willexert a pressure of 0.6 psi. on a molded cylindrical pellet of thepolymer resting on another iron plate. The height of the pellet ismeasured before and after a period of heating in an oven and the resultsreported as percent compression set, i.e., (change in height/originalheight) l00. The pellets are in. in diameter and /2 in. in height, ascalled for by ASTM D945-59.

EXAMPLES 7-9 Production of Ethylene/Propylene/1,4-Hexadiene/Norborneo-Norbornene Copolymer Polymer samples are prepared according tothe method described in Examples 2-5. Norborneo-norbornene is preparedaccording to the method of J. K. Stille, J. Am. Chem. Soc., 8], 4273(1959). The norborneo-norbornene is passed through a short column ofneutral grade Woelm alumina and diluted with perchloroethylene toprepare a solution approximately .025 Molar in diene. The desiredquantity of diene solution is then added to the reaction flask at thetime described in Table IV by means of a hypodermic syringe.

It can be seen from the results in Table IV that only a very smallquantity of norborneo-norbonene is necessary to profoundly alter thebulk viscosity characteristics of the sulfur-vulcanizable terpolymer.

An E/P/norborneo-norbornene terpolymer is prepared by the method ofExamples 2-9 except that no 1,4-hexa- TABLE 11 Wt. percent Moles]Wallace Reaction Yield, Propyl- 1,4-hexakg- 4th p las- Cold VanadiumExample time, min. grams ene diene 4th monomer monomer ticlty mus. flowcatalyst 2 Control 20 20. 5 49 3. 6 0 30 2. 17 47 20 23. 5 51 3. 21,4-pentadiene 0.13 33 2. 26 46 V(AA); 20 21. 0 49 3. 5 0. 29 39 2. 3318 15 15. 5 48 8. 5 0 37 2. 17 57 15 16.0 51 3. 7 1,20-henelc0sadiene...0. 03 36 2. 20 37 V(AA); 15 14. 0 48 3. 9 0. 07 51 2. 26 2 15 12. 0 463. 8 0 30 2. 67 55 15 11. 5 49 3. 8 1,7-octadiene--.-;-:.;.:-:..-. 0.0938 2. 22 8 V0 013 15 12. 0 45 3. 9 0. 21 59 2. 69 0 15 13. 5 45 4. 2 026 2. 12 71 15 14. 5 50 4. 2 5-(5-hexenyl)norb0rnene..;:. 0. 017 36 1.99 14 V(AA); 15 16. 5 53 3. 7 0. 031 2. 68 2 TABLE IV.PROD UCTION (NBNB)COPOLYMER Quantity Reaction N BNB added, Wallace Percent Wt. per- Time,Temp, Method of moles/kg. Cold plas- Yield, propylcent 1,4- Example min.C. NBNB addn. polymer flow tieity flinh. grams ene hexadiene 7 control10 65 32. 7 2. 33 10 44 3. 6 10 029 2 70 2. 63 8. 44 4. 1 l0 0 32.2 2.07 11. 0 50 3. 2 026 55 2. 18 9. 5 43 3. 9 0 19. 5 1. 68 16 52 3. 6 15029 1. 70 17 53 3. 7 15 059 34 1. 86 17 51 3. 9 15 0. 10 39. 5 l. 86 1548 3. 6

TABLE V.-CONTROL POLYMERS CONTAINING NO DIOLEFIN HAVING ONLY ONE READILYPOLYMERIZ- ABLE DOUBLE BOND Percent Moles/kg. Yield, propy- Brominenorborneo- Control g. wins, lene equiv. norbornene 25 Z 18 1. 64 7O 0.04 0 Y- 20 1. 74 68 0. 04 O. 037

Neither control Y nor Z is curable by sulfur curing ingredients.

These results indicate that there is no contribution to the unsaturationnumber of the polymer by the norbonreonorbornene, and that theincorporation of dienes with two readily polymerizable double bonds inthe concentrations of the compositions of this invention does not confersulfur curability on ethylene-propylene copolymers. Norborneo-norborneneis highly reactive and both double bonds react almost completely. Incontrast, aliphatic dienes are not as reactive and they may leave aconsiderable residue of unsaturation in the polymer.

EXAMPLE 10 Production of E/P/1,4Hexadiene/Bicyclo(2.2. 1 -Hepta-2,5-Diene (2,5-Norbornadiene) Copolymer TABLE VI Wallace Yield Molesbicyclo-heptadiene/kg. polymer plas. flinh. (g s) It can be seen thatwith increasing bicycloheptadiene content that the bulk viscosity wentup rapidly whereas there was only a minimal increase in inherentviscosity.

EXAMPLE 11 Production of E/P/1,4-Hexadiene/Dimers of Bicyclo- HeptadieneCopolymers Polymer samples were prepared as in Example No. 10. Thebicyclo(2.2.1)-hepta-2,5-diene dimers were prepared by heatingbicycloheptadiene with a bis(triphenyl phosphite) nickel dicarbonylcatalyst for 36 hrs. in toluene. The

isomeric dimers so prepared have the structure designated thus:

The results are reported in Table VH.

TABLE VII Wallace Moles/kg.4th monomer plas. flinh.

EXAMPLE 12 Preparation of High Diene Content E/P/HD/OD Tetrapolymer To a2-liter resin kettle equipped with a mechanical stirrer, thermometer,addition funnel and syringe inlet, and dried thoroughly with a heat gununder a nitrogen atmosphere, is added 884 ml. of anhydrous hexane, 116ml. of 1,4-hexadiene and 1.0 ml. of 1,7-octadiene. 'Ihe stirred mixtureis cooled to -17- 3 C. while being saturated with ethylene fed at a rateof three gram moles per hour and propylene fed at a rate of 0.1 grammole per hour. A 2.33 ml. portion of pure diisobutylaluminum chloride isadded followed by a dropwise addition of 20 ml. of a 0.1 M solution ofVCL, in perchloroethylene over a period of 21 minutes. The temperatureis maintained at -17i3 C. for 30 minutes after the addition of VCL; isbegun. The polymerization is stopped with the addition of a hexanesolution containing about 3.0 ml. of isopropanol and 0.5 grams of4,4'-thio-bis-(6-tert-butyl-meta-cresol). The isolated polymer contains8.4% of propylene by weight and 2.61 moles/kg. of ethylenicunsaturation.

EXAMPLE 13 A. Preparation of a,w-Diallylpolybutadiene A 2-liter flaskwas fitted with a magnetic stirrer, a thermometer, a condenser and twoaddition funnels (one of which had cold fingers" suitable for coolingwith crushed solid carbon dioxide). After the entire assembly had beendried with heat under a nitrogen atmosphere, one liter of anhydrous,reagent grade tetrahydrofuran, fifty grams of reagent grade naphthalene,and 2.1 grams of clean lithium ribbon were added in turn to the flask.The temperature was held at 2530 C. until the lithium was completelydissolved (2.6 hours). Then the solution was cooled to 45 C. Butadiene(92 ml.), which had been dried by passage through a molecular sievetower, was collected in the cold addition funnel and added to the flaskduring a 15-minute period. The resulting solution was allowed to warm to-10 C. in thirty minutes and held at 10i5 C. for one hour to preparea,w-dilithio poly- 0 butadiene. Then a total of thirty-nine millilitersof anhydrous allyl chloride was added dropwise while the temperature waskept at 0:5 C. The deep red color disappeared when twenty-threemilliliters of allyl chloride had been added. Finally, a solution of0.139 g. of 4,4'-di thiobis(3-methyl-6-tert-butylphenol) in a mixture ofisopropanol/hexane (1:8 by volume) was introduced. After the solventshad been evaporated at reduced pressure, the resulting residue was steamdistilled until all the naphthalene was removed. The viscous residue wasseparated from the water phase and finally dried at reduced pressure at100 C. The a,w-diallylpolybutadiene obtained thereby weighed 74.5 gramsand had a number-average molecular weight of 480 (by vapor phaseosmometry) B. Preparation of E/P/l,4-Hexadiene/a,w-DiallylpolybutadieneTetrapolymer The polymerization was carried out continuously by using aliquid-full, 1.2-liter, stainless steel reactor maintained at a pressureof 100 p.s.i.g. The following feed rates were established:

Ethylene, 2.365 gram-moles per hour; propylene 4.55 gram-moles per hour;1,4-hexadiene, 0.207 gram moles per hour; a,w-diallylpolybutadiene, 2.56grams per hour; VOCl .076 millimole per hour; triethylaluminum, 1.39millimoles per hour; diethylaluminum chloride, 0.793 millimoles perhour; benzotrichloride, 1.95 moles per hour; hydrogen, 2.25 millimolesper hour; and hexane, 1.903 liters per hour.

The average residence time was thirty minutes. The reactor temperaturewas maintained at 35 C. by external cooling. Polymer was produced at anaverage rate of 100.6 grams per hour. The reactor effiuent wasdischarged into a flasher where unreacted ethylene and propylene wereallowed to evaporate at atmospheric pressure. The residual polymersolution was then mixed with a solution of4,4'-thio-bis(3-methyl-6-tert-butyl phenol) in an isopropanol-hexanemixture (1:8 by volume) before catalyst residues were removed withdilute acetic acid and water washes. Hexane was removed by evaporationon a drum drier. The isolated tetrapolymer had the following monomerunit composition: 2.5% a,w-dially1polybutadiene, 38.8% propylene, 3.1%1,4-hexadiene, and 55.6% ethylene (by weight). The inherent viscosity ofthe polymer was 1.86 (measured at 30 C. on a solution of 0.1 gram oftetrapolymer in 100 ml. of tetrachloroethylene); the Mooney viscosity(ML-1+4 at 121 C.) was38.

The branched-chain elastomeric copolymers of this invention have beenfound to be especially useful in blends with polyunsaturated elastomerssuch as natural rubber and the synthetic diene elastomers. It is knownin the art that the EPM and EPDM elastomers confer a measure of ozoneresistance on such' blends, but it has surprisingly been found that thebranched-chain tetrapolymers of this invention are much more effectivethan the prior art terpolymers as illustrated by the followingExperiments.

EXAMPLE A The following compositions are prepared by standard laboratoryrubber milling procedure and vulcanized in test slabs for minutes at 163C.

Specimens of the vulcanizates are tested for ozone resistance by ASTMmethod D1149, at 50 and 300 parts ozone per 100 million (p.p.h.m.). Asshown by the data of the Table VIII, the octadiene-modified tetrapolymergives a blend with natural rubber having substantially better ozoneresistance than the prior art EPDM terpolymer.

TABLE VIII.OZONE RESISTANCE OF :20 NATURAL RUBBER/COPOLYMER BLENDS 110=no efiect. 8=noticeable visual cracking. 4=heavy cracking. 0=break.

EXAMPLE B A masterbatch was prepared in a Farrel Midget Banbury Mixer(having a 250 ml. void) by combining 20 grams of the tetrapolymer ofExample 13B, 50 grams of natural rubber, 30 grams of neoprene, type W,3.5 grams of zinc oxide, 25 grams of FEF carbon block, and 3.0 grams ofCircosol Light Oil. Then the following curing ingredients consisting of0.5 gram of 2,2'-dithiobisbenzothiozole, 0.35 gram of diphenylguanidine,2.0 grams of stearic acid and 1.3 gram of sulfur were added at about 50C. on a 4 x 8 rubber mill. Slabs, made from the resulting stock, werecured for 15 minutes at 320 F. between Mylar polyester sheets. Dumbellswere cut with a die and clamped in the Dynamat attachment in a chamberat 40 C. where the ozone concentration was maintained at 0.5 p.p.m. andthe samples were flexed for a period of up to 24 hours.

The tetrapolymer of Example 13B imparted good ozone resistance to theblends, whereas a control blend substituting a tripolymer of ethylene,propylene and 1,4-hexadiene (made by a similar process) for thetetrapolymer displayed poor ozone resistance.

The branched-chain elastomeric copolymers of this invention have beenfound to be especially useful in blends with polyunsaturated elastomers,such as natural rubber, and the synthetic diene elastomers. Particularlyuseful are styrene/butadiene elastomers (e.g. SBR containing 23.5%styrene by weight), polybutadiene, and butadiene/acrylonitrile, (e.g.NBR having 20 45% acrylonitrile). Natural rubber, styrene/butadiene, andpolybutadiene are preferred.

1 Naphtenic petroleum 011.

What is claimed is:

1. A sulfur-curable ozone-resistant composition comprising about 10 to30 parts by weight of a copolymer of (a) from 25% to 75% by weight ofethylene units, (b) units derived from a C -C polyolefin containing twopolymerizable double bonds, said polyolefin units being present in anamount resulting from the addition to the reaction mixture from whichsaid copolymer is formed of about from 0.01 to 0.5 gram mole perkilogram of copolymer formed of said C -C polyolefin, the amount of thepolyolefin not to exceed 15% by weight of the copolymer, (0) sufiicientunits of a non-conjugated diolefin containing only one polymerizabledouble bond selected from the group consisting of (1) an aliphaticdiolefin, and (2) a cycloaliphatic compound having a oneor two-carbonbridged ring structure to provide 0.1 to 4.0 gram moles per kilogram ofcarbon-carbon double bonds derived from the diolefin, and (d) theremainder of said copolymer being propylene units, and about 90 to 70parts by weight of a polyunsaturated elastomer selected from naturalrubber or a synthetic diene elastomer.

2. Composition of claim 1 wherein the polyunsaturated elastomer isnatural rubber.

3. A composition of claim 1 wherein polyolefin (b) has two strained ringdouble bonds a cycloaliphatic structure.

4. A composition of claim 1 wherein polyolefin (b) has two unhinderedterminal double bonds.

5. A composition of claim 1 wherein polyolefin (b) has one strained ringdouble bond in a cycloaliphatic structure and one unhindered terminaldouble bond.

6. A composition of claim 1 wherein the synthetic diene elastomer isstyrene/butadiene.

7. A composition of claim 3 wherein diolefin (c) is an aliphatic olefin.

8. A composition of claim 3 wherein diolefin (c) is a cycloaliphaticolefin having a oneor two-carbon bridge ring structure.

14 9. A composition of claim 1 wherein polyolefin (b) is norbornadiene.

10. A composition of claim 9 wherein diolefin (c) is 1,4hexadiene.

11. A composition of claim 9 wherein diolefin (c) is 5-ethylidene-Z-norbornene or dicyclopentadiene.

12. A composition of claim 9 wherein the polyunsaturated elastomer isnatural rubber.

References Cited UNITED STATES PATENTS 3,554,988 1/ 1971 Emde et a1260-8018 3,444,146 5/1969 Valvassori et a1. 26080.78 3,224,985 12/ 1965Gladding et a1 260-5 3,443,619 5/1969 Kindle 26()-5 3,492,370 1/ 1970Wirth 2065 JOHN C. BLEUTGE, Primary Examiner US. Cl. X.R.

